This proposal has three distinct areas of investigation: 1) The structure and biosynthesis of membrane immunoglobulin and secreted immunoglobulin in normal and in leukemic lymphocytes; 2) the nature of T cell receptors in contact sensitivity; 3) the structure and function of Fc receptors on lymphocytes and macrophages. The structural feature of membrane Ig which permit its integration into the plasma membrane will be investigated with the help of radioisotope and microsequencing methods. The biosynthetic pathways of membrane IgM and IgD and secreted Ig will be studied using biosynthetic labeling methods on intact cells and in cell-free system, and an ultrastructural analysis using the immunoperoxidase procedure. These methods will also be used to explore the possible cellular and/or Ig structural defects associated with the inability of leukemic lymphocytes to secrete intact Ig. The antigen receptor on T cells responsible for delayed type hypersensitivity to the contactant DNFB will be isolated using affinity methods dependent upon the receptor's capacity to bind antigen, anti-idiotype and anti-VH framework reagents. Functional studies that will be carried out include; the regulation of Ig secretion by plasma cells, the regulatory role of Fc receptors on B cell differentiation, the mechanism of Ig transport across gut epithelium, and the interaction of Fc receptors with intracellular cytoskeletal elements.